Question

locate cs, sr, rb, and ba on the periodic table. which would you expect to be the least reactive? cs ba rb sr

Explanation:

• Reactivity of metals in the same period (row) of the periodic table: As we move from left to right across a period, the reactivity of metals generally decreases.
• Position of the elements: Cs (Cesium) is in Group 1 (most reactive metal group in this context among the given), Rb (Rubidium) is also in Group 1 but above Cs. Sr (Strontium) is in Group 2 and Ba (Barium) is also in Group 2 but below Sr. Group 2 metals are less reactive than Group 1 metals. Among Group 2 metals, reactivity increases down the group. So Sr (Strontium) is less reactive than Ba.

Answer:

Sr